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Inverse spinel structures have a different cation distribution in that all of the A cations and half of the B cations occupy octahedral sites, while the other half of the B cations occupy tetrahedral sites. An example of an inverse spinel is Fe 3 O 4, if the Fe 2+ (A 2+) ions are d 6 high-spin and the Fe 3+ (B 3+) ions are d 5 high-spin.
Cuprospinel is a mineral.Cuprospinel is an inverse spinel with the chemical formula CuFe 2 O 4, where copper substitutes some of the iron cations in the structure. [4] [5] Its structure is similar to that of magnetite, Fe 3 O 4, yet with slightly different chemical and physical properties due to the presence of copper.
However the structure is not an ordinary spinel structure, but rather the inverse spinel structure: One eighth of the tetrahedral holes are occupied by B cations, one fourth of the octahedral sites are occupied by A cations. and the other one fourth by B cation. It is also possible to have mixed structure spinel ferrites with formula [M 2+
Other known ferrimagnetic materials include yttrium iron garnet (YIG); cubic ferrites composed of iron oxides with other elements such as aluminum, cobalt, nickel, manganese, and zinc; and hexagonal or spinel type ferrites, including rhenium ferrite, ReFe 2 O 4, PbFe 12 O 19 and BaFe 12 O 19 and pyrrhotite, Fe 1−x S. [12]
A related family of industrially useful "hexagonal ferrites" are known, also containing barium. [1] In contrast to the usual spinel structure, these materials feature hexagonal close-packed framework of oxides. Furthermore, some of the oxygen centers are replaced by Ba 2+ ions. Formulas for these species include BaFe 12 O 19, BaFe 15 O
Zinc ferrites are a series of synthetic inorganic compounds of zinc and iron with the general formula of Zn x Fe 3−x O 4. Zinc ferrite compounds can be prepared by aging solutions of Zn(NO 3 ) 2 , Fe(NO 3 ) 3 , and triethanolamine in the presence and in the absence of hydrazine , [ 1 ] or reacting iron oxides and zinc oxide at high temperature.
The transparent red spinels were called spinel-rubies [14] or balas rubies. [15] In the past, before the arrival of modern science, spinels and rubies were equally known as rubies. After the 18th century, the word ruby was only used for the red gem variety of the mineral corundum, and the word spinel came to be used. [16] "
The structure is inverse spinel, with O 2-ions forming a face-centered cubic lattice and iron cations occupying interstitial sites. Half of the Fe 3+ cations occupy tetrahedral sites while the other half, along with Fe 2+ cations, occupy octahedral sites. The unit cell consists of thirty-two O 2-ions and unit cell length is a = 0.839 nm. [15] [16]